Electrol



Oct. 11'", 1927. 1,645,085

LE RUE P. SENSING ELECTROLYTIC RECTIFIER Filed Aug. 31. 1925 IIHE VESM/Hnwntov ,5 3 5 P- BEME/ME Z3101, ow f Guam,

Patented Oct. 11, i927.

UNITED STATES PATENT OFFICE.

LE RUE P. BENSING, OF CLEVELAND. OHIO, ASSIC ENOB OF ONE-HALF TO GEORGEP. KOELLIKER, OF CLEVELAND HEIGHTS, OHIO.

ELECTROLYTIC RECTIFIER.

Application filed August 31, 1925.

My invention relates to electrolytic rectifiers, and is an improvementin the electrolytic rectifier disclosed in my application filed May 6,1925, Serial Number 28,524, in which I use a fluoride 'as an electrolytetogether with magnesium, the electrolyte consisting of approximatelytwenty-five per; cent potassium fluoride and seventy-five percent water.In the present case my object is to provide an electrolytic rectifier inwhich a fluoride electrolyte -may be used together with a metallicanode, for example an anode of lead or containing lead. There are manyuses for electrolytic rectifiers in which the current density on theanode is relatively high, and I find that with a fluoride electrolytethere is in time a certain tendency toward disintegration of a metallicanode if the current density becomes. too great and the temperature ofthe rectifying cell becomes excessive. Under such conditions I find amagnesium or silicon cathode functions satisfactorily, that is, it has along life, a thin adherent surface coating, gives high electricalefliciency, etc, especially cathodes of magnesium and silicon used in afluoride electrolyte. On the other hand, the use of lead or othermetallic anodes in that connection offered certain difiiculties, butlead anodes are relatively cheap and easy to manufacture, and I havedisco ered that they may be used as advantageously in a fluorideelectrolyte as the magnesium or silicon cathodes mentioned, providing analkaline media is also used, and where other metals are present additivereagents may also be used, all as hereinafter described and moreconcisely pointed out in the claims. In the accompanying drawing, thesingle figure is a sectional view exemplifying one form of anelectrolytic rectifier embodying my in vention.

Thus, I find in using lead, its alloys, and compounds, that a certainamount of alkalinity of the fluoride electrolyte is required to preservethe lead anode. If, for example, a neutral or acid fluoride is used,enough alkali, a fixed hydroxide or carbonate, must he added to bringthe electrolyte alkaline to litmus. An excess of alkali is then addedwhich may vary from a fraction of one percent to several percentdepending in large measure upon the nature of the composition of theanode as well as the current density Serial No. 53,750.

under which it is operated. The function of the alkali may be consideredas neutralyzing the small amounts of nascent fluorine liberated at thesurface of the anode.

Other steps may be'taken for accomplish- .mg this same purpose;forexample, an acid or neutral fluoride electrolyte may be used as arectifying solution together with a carbon or graphite anode. Afteroperating such a rectifier for a given period of time a certain amountof alkalinity is developed. The amount maybepredetermined by the lengthof time the rectifier'is operated or by the eurrent density of theanode. -When the desired or proper alkalinit of the solution is reacheda suitable metal ic anode may be substituted for the carbon or graphiteelectrode and the rectifier .wilLfunction efficiently in the same way asif a fixedalkali was added. Y, I I. I

Therefore I do not desire. -to .limit myself as the particular mode ormanner, inwhic'h the alkalinity is produced in the electrolyte, havingfound thru experimentation that metallic lead will act as a permanentanode in electrolytes that have been prepared in both ways as herein setforth. I have also found that alloys of lead function similar to themetal itself in such electrolytes, a good example bemg a copper-leadalloy. WVhen the current densities are not too high and the temperatureof the cell is within the proper limits a thin adherent coating isformed on the anodes when employed under the above conditions.

I also find when a lead alloy, containing an element which is soluble inthe fluoride electrolyte is used as herein described. that such alloywill function properly as an anode without deterioration, providingsmall amounts of an acid, the salt or conipound of an acid, are added tothe fluoride electrolyte. A very good example of this phenomenon is thestandard storage battery alloy which consists of an alloy of antimonyand lead. This alloy will not give very good service under appreciablecurrent densities when used with an alkaline fluoride electrolyte,excepting when a trace of sulphuric acid, its salts or compounds, areadded to the alkaline fluoride electrolyte. In the latter event thedisintegration of the anode is prevented.

From the foregoing it will be deduced that-a certain chemical balancemay be produced in a rectifier using enough fluoride to protect thecathode and enough alkali to protect :the lead base of the anode andthat with an anooe of leadaaid copper, or antimony and lead, and similaralloys, an additive reagent prevents solution of the alloying elementand the lead. For example, two percent, more or less, of a fixedulk-al-i added to a fluoride electrolyte will protect a lead anode, andthe addition of three-or four drops of concentrated sulphuric acid, or asoluble sulphate may beused asa reagent with a total of 250 cub'iecentimeters of the alkaline fluoride electrolyte to protect an anodemade of lead alloy, say antimony and lead. In either case, a strongthin, adherent protective 'film'or' coating is toduced upon the surfaceof the anodether'eby assuring a long life and high etficiency thereto.

ant to aqueous hydroxide solutions and vforms a slightly soluble orinsoluble-fluoride.

What I claim, is:

l. An electrolytic rectifier, comprising a lead anode, a cathode, and anaqueous fluoride electrolyte having a small per cent of alkalinity, theflum'ide being in excc$ .ot the alkali and at least fire percent of theaqueous solution.

2. In :a-u electrolytic rectifier, a cathode comprising magnesium, ananode comprisingl'lead, and an v,a'lkalesceut fluoride elevtrolyte, thefluoride being in excess of the alkali,

3. In an electrotyt ie rectifier. a metallic anode resistant toalka'lies and fluorides, in

combination with an alkaline aqueous luor1de,.tl i'e fiuonide being inpreponderahing amount compared with all other salts pres- 'ent'.

4. In an electrolytic rectifier, an anode made of lead alloy, and analkaline aqueous fluoride-electrolyte, containing a trade:

or sulphuric acid, the fluoride being in preponderating amount:oonxpa-r-ed with all other salts present.

In an electrolytic rectifier, a potassium fluoride solution, a cathodeof magnesium, the fluoride "being im excess .of one percent. and analkir'li slightly in excess bf the amount 1' uired -to bring the.clectzrol-ylr alkaline to tmus.

In testimony nheneof'I afiixniysigawturc.

LE P. BENSING,

